The goals of this study are to study the effects of isoproterenol and/or testosterone on the regeneration of rat submandibular glands after partial extirpation. A portion of the left submandibular gland will be surgically removed from each animal. Isoproterenol will be given to one group of animals after surgery, and testosterone will be given to a second group. A third group will be given both isoproterenol and testosterone. Appropriate controls will be run with each group. Effects of the agents on the glands will be studied using histologic, histochemical, and electron microscopic techniques. Additionally some control and experimental animals will be given colchicine and mitotic indices will be determined for the parenchymal elements.